/**
 *    Copyright 2009-2015 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.apache.ibatis.logging.jdbc;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.ResultSet;
import java.sql.Statement;

import org.apache.ibatis.logging.Log;
import org.apache.ibatis.reflection.ExceptionUtil;

/**
 * Statement proxy to add logging(Statement代理类添加日志功能)
 * 
 * @author Clinton Begin
 * @author Eduardo Macarron
 * 
 */
public final class StatementLogger extends BaseJdbcLogger implements InvocationHandler {

	private Statement statement;

	private StatementLogger(Statement stmt, Log statementLog, int queryStack) {
		super(statementLog, queryStack);
		this.statement = stmt;
	}

	@Override
	public Object invoke(Object proxy, Method method, Object[] params) throws Throwable {
		try {
			// 判断方法定义的类是否和当前的Object一样
			if (Object.class.equals(method.getDeclaringClass())) {
				return method.invoke(this, params);
			}
			   //如果是当前EXECUTE_METHODS中存在的值
			if (EXECUTE_METHODS.contains(method.getName())) {
				// 判断是否开启debug级别
				if (isDebugEnabled()) {
					// 记录日志
					debug(" Executing: " + removeBreakingWhitespace((String) params[0]), true);
				}
				// 判断是否是查询
				if ("executeQuery".equals(method.getName())) {
					ResultSet rs = (ResultSet) method.invoke(statement, params);
					//如果不为空就打印添加一个日志版本
					return rs == null ? null : ResultSetLogger.newInstance(rs, statementLog, queryStack);
				} else {
					return method.invoke(statement, params);
				}
			} else if ("getResultSet".equals(method.getName())) {//如果方法名称和 getResultSet一致
				ResultSet rs = (ResultSet) method.invoke(statement, params);
				return rs == null ? null : ResultSetLogger.newInstance(rs, statementLog, queryStack);
			} else if ("equals".equals(method.getName())) {//如果方法名称和 equals一致
				Object ps = params[0];
				return ps instanceof Proxy && proxy == ps;
			} else if ("hashCode".equals(method.getName())) {//如果方法名称和 hashCode一致
				return proxy.hashCode();
			} else {
				return method.invoke(statement, params);
			}
		} catch (Throwable t) {
			throw ExceptionUtil.unwrapThrowable(t);
		}
	}

	/*
	 * Creates a logging version of a Statement(给Statement添加一个日志版本)
	 *
	 * @param stmt - the statement
	 * 
	 * @return - the proxy (返回的是代理的Statement对象)
	 */
	public static Statement newInstance(Statement stmt, Log statementLog, int queryStack) {
		// 添加日志版本
		InvocationHandler handler = new StatementLogger(stmt, statementLog, queryStack);
		ClassLoader cl = Statement.class.getClassLoader();
		return (Statement) Proxy.newProxyInstance(cl, new Class[] { Statement.class }, handler);
	}

	/*
	 * return the wrapped statement
	 *
	 * @return the statement
	 */
	public Statement getStatement() {
		return statement;
	}

}
